Upon the surgical removal of a hollow vessel portion, e.g. in the course of an intestinal resection due to a bowel part afflicted with a tumor, the two hollow vessel portions have to be connected to each other at their opened ends such that a continuous pathway is produced. This is referred to as an end-to-end anastomosis. As a standard procedure, the two opened ends are re-sewn to each other, e.g. by means of medical staple-type suture devices.
Especially in the case of procedures on the small and large intestines, leaking suture connections (suture insufficiency) occur from time to time, which are associated with a severe progression of the disease and also with a high mortality rate.
An alternative for sewing the hollow vessel portions to each other or clipping them with medical staples is Tissue Fusion Technology (TFT). Tissue fusion by means of radio frequency technology (RF) is based on the denaturation of proteins which are contained in many types of tissue. This allows the welding of collagen-containing tissue. During the welding procedure, the tissue is heated up to temperatures above protein denaturation temperature and together with the intra- and extra-cellular matrix is converted to a gel-like condition. After compressing the tissue surfaces, the liquefied tissue cools down to a fused mass, causing a reliable connection of the tissue. Such an electrosurgical instrument is known from EP 2 335 608 A2.
For the purpose of welding the hollow vessel portions, a high-frequency current is applied to the tissue which is gripped between two tool parts (clamping elements) which are movable relative to each other, the current flowing between electrodes on the two tool parts in a bipolar manner. In order to avoid a failure of the sealing or welding, the parameters acting on the tissue have to be detected and controlled. To ensure this, precise monitoring of temperature, pressure, tissue impedance, distance and position is required. The pressure which is exerted on the tissue gripped between the two tool parts is generated by a lever mechanism or a rotary knob on the proximal end of the instrument and transmitted to the two tool parts via a force transmission element in the hollow shaft tube.
From U.S. Pat. No. 5,205,459 B there is known a surgical instrument for an end anastomosis, in which the tissue ends to be connected are connected to each other by medical staples. For the purpose of transmitting the forces from the distal actuation device to the proximal staple tools, force transmission elements are provided in the hollow shaft and are arranged in a plastic hollow section within the shaft. The force transmission elements comprise a plastic hollow section for transmitting compressive forces and a cable running in the plastic hollow section for transmitting tensile forces.
A problem with the mentioned surgical instruments comprising a thin shaft tube, in particular with electrosurgical instruments, is that the force transmission elements and any electric supply lines and other supply elements must be laid through the thin trocar shaft.